Growers increasingly use urea-based fertilizers because ammonium nitrate often isn’t available, the researchers point out. But urea is susceptible to losses from ammonia volatilization. Studies have shown that ESN (Environmentally Smart Nitrogen) reduces those losses, but it releases nitrogen too slowly for early forage harvests, they say.

At two locations, they applied 300 lbs/acre of nitrogen in two applications of urea-ESN blends that were 0%, 25%, 50%, 75% and 100% ESN. Conventional treatments of 300 lbs/acre of ammonium nitrate or urea were also applied in four equal amounts.

The 50% and 75% ESN treatments performed about the same as ammonium nitrate. They produced 10,426 and 10,035 lbs of dry matter per acre, respectively, vs. 9,461 lbs for urea-only. Their total nitrogen recovery, grass crude protein content and TDN were also higher than comparable figures from the urea-only treatment.

“These results support the development of a recommendation of blending ESN at a rate of 50% and 75% with urea as a substitute for ammonium nitrate,” the researchers wrote.